"The Kremlin-controlled United Russia party holds two thirds of seats in the Duma, enough to pass legislation single-handedly."
I am not aware of any efforts in the US to ban third parties or third pary candidates. The vast majority of third party candidates lose, but they are not prevented from running. Putin's Unity party is attempting to ban third parties altogether.
Next time do some homework. Either you have poor reading comprehension skills or are ignorant of such things or know the facts full well but are here to advocate a position and thus distort truth for that agenda.